This invention relates to electric power storage, through power interface electronics and electromechanical energy conversion, in the inertia of a spinning flywheel, and by reciprocal means, stored kinetic energy conversion to electric power. The various component elements of the invention include: A high-speed motor/generator, with cooperative power electronics and magnetic bearings, electronic feedback control servos to stabilize the magnetic bearings, a vertical-axis flywheel, integral with the motor/generator rotor and rotatable magnetic bearing elements, to store kinetic energy, a vacuum enclosure to reduce air drag, mechanical backup bearings that are not engaged during normal service, and a stationary energy-absorbing installation site to safely house the flywheel and its enclosure.
As also illustrated in the above-referenced United States patents, such means as rechargeable electrochemical batteries offer some usages, but encounter huge problems involving key issues such as storage space, leakage and longevity. Therefore flywheel driven systems may offer distinct advantages over such systems. However, as flywheel power storage system designs have evolved from smaller, physically limited structures with minimal storage capacity to the high capacity systems employing industrial sized magnetic members prevalent today, material restrictions and other such factors inherent with have arisen. Said considerations must be overcome in order to facilitate reaching the maximal energy storage and output to render flywheel energy storage systems a viable alternative.
In modern applications, due to the need for extremely large magnetic arrays and magnetic members, current manufacturing capabilities restrict magnetic arrays to structures containing joined magnetic segments. Due to the inherent discontinuities in flux density across these segments occurring upon interface of the rotor and stator, if faced directly with rotor, the permanent magnet array will induce eddy current and excess heat upon the rotor. Thus, in order to address this shortcoming, what is needed is a mechanism and/or system which works to eradicate these problems by vitiating or smoothing out the discontinuities from the segments.
Additionally, in modern larger applications, magnetic force generated either by permanent magnet or electromagnet or the combination of both is used to lift the rotor in a flywheel system. Magnetic force generated by a pair of stationary stator and rotor is normally highly sensitive to the air gap separating the stator and rotor. High sensitivity implies low magnetic force as the gap is large and excessively high force as the gap is small. Lower force at the large gap requires designs with either stronger magnets or higher current to lift the rotor, and excessively high force at small gap would potentially damage the parts under the fault conditions.
Previous failure of high capacity flywheel systems often is found to be triggered by overloading and overheating of the touchdown ball bearing. When utilizing a pure electromagnet lift magnet, failure offer occurs as the electrical power is tripped during normal operation due to the high lifting force requirement. As the lifting force dissipates, the heavy rotor will then sit on the ball bearings, and thus, due to the heavy load, will heat up the ball bearings in a short expense of time. Thus, as the ball bearing fails, the high speed rotor loses the mechanical support, and rotates basically out of round, contacting the casing. Thus, wear, catastrophic at times and even explosions within the casing may occur.
Further, in systems utilizing magnetic force generated either by a permanent magnet or electromagnet or the combination of both to lift the rotor, the magnetic force generated by a pair of stationary stators and rotor is normally highly sensitive to the air gap separating the stator and rotor. High sensitivity implies that low magnetic force occurs when the gap is large in magnitude and excessively high force occurs when the gap is small in magnitude. The larger gap condition at which lower force occurs requires designs with either stronger magnets or higher current to lift the rotor; whereas, on the other hand, the excessively high force at small gap could potentially damage parts or the overall system under fault conditions.
Therefore, when investigating the typical lift magnet design, what is needed is a design that can provide magnetic force with low gap sensitivity, for the conditions at which the magnetic force is moderately higher at the large gap configuration and significantly lower at the small gap configuration. Additionally, what is needed is a system, mechanism or method of operation, which minimizes the load on the ball bearings in the case where the rotor drops on the bearing for any potential failure mode. Also needed is a system to prevent the high speed rotor form sticking to the stator under any potential failure mode while also minimizing the electrical power used in the lift magnet system to minimize the heat generation which lends to superior control of the rotor.